Centrifugally nonresponsive electrical snap switch



March 8, 1949. R. K. TIEDEMAN CENTRIFUGALLY NONRESPCNSIVE ELECTRICALSNAP SWITCH '3 Sheets-Sheet 1 Filed Oct. 1, 1945 (Ittorneg March 8,1949. I R. K. TIEDEMAN 2,463,659

CENTRIFUGALLY NONRESPONSIVE ELECTRICAL SNAP SWITCH Filed Oct. 1 1945 3Sheets-Sheet 2 Snuenlov .ZFMe/TK fizzle/71412 Cxttomeg March 8, 1949. RK, TlEDEMAN 2,463,559

CENTRIFUGALLY NONRESPONSIVE ELECTRICAL SNAP SWITCH Filed Oct. .1, 1945 sShets-Sheet 5 3 nventor Cittorneg Patented Mar. 8, 1949 CENTRIFUGALLYNONRESPONSIVE ELECTRICAL SNAP SWITCH Robert K. Tiedeman, UpperMontclair, N. J assignor to Curtiss-Wright Corporation, a corporation ofDelaware Application October 1, 1945, Serial No. 619,530

9 Claims. 1

This invention relates to an electrical switch mechanism and moreparticularly to an improved switch mechanism which has particularapplication, for example, in an aircraft propeller assembly of theelectrically operable controllable pitch change type.

The invention has particular reference to an improved switch mechanismof the dual contact type wherein a resilient link toggle arrangement isadapted to be operated to maintain an electrical circuit either open orclosed.

In a known electric controllable pitch propeller assembly for aircraft,a plurality of switch mechanisms are associated with the hub end of thespeed reducer housing for operation in suitable manner to open thecircuit of the pitch change electric motor when the propeller bladesreach limiting low, high, feather or reverse pitch angles.

The principal object of the invention is to provide improved switchmechanisms operable for the purpose stated which have high currentcarrying capacity, which provide a large breaker gap between the fixedand movable contacts, which afford rapid operation of the movablecontacts toward and away from the fixed contacts, and which are notadversely affected by the presence of lubricants.

A further object of the invention is to provide an improved switchmechanism which, at its cooperative contacts, is not adversely affectedby centrifugal force resulting from high propeller H. P. M.

With these and other objects in view, the invention resides in the novelconstruction, combination, and arrangement of parts, the novel featuresof which are set forth with particularity in the appended claims, theinvention itself, however, both as to its organization and its method ofoperation, together with additional objects and advantages thereof,being best understood from the following description of a specificembodiment, when taken in connection with the accompanying drawings, inwhich:

Figure 1 is a fragmentary, side elevational view, partly in section,illustrating a switch mechanism, constructed in accordance with theinvention, associated with the speed reduced mechanism of an electric,controllable pitch change aircraft propeller assembly;

Fig. 2 is an elevational view illustrating the inner end of the switchmechanism;

Fig. 3 is a vertical sectional view of the switch mechanism taken on theline 33 of Fig. 2 with the switch contacts in closed position;

Fig. 3a is a fragmentary view illustrating cooperating parts of myswitch mechanism as the same is shown in Fig. 3;

Fig. 4 is a view corresponding with Fig. 3 and illustrates the initialcontact of a switch-operating member with a switch mechanism constructedin accordance with the invention;

Fig. 4a, is a fragmentary view illustrating cooperating parts of myswitch mechanism as the same is shown in Fig. 4;

Fig. 5 is a view corresponding with Figs. 3 and 4, the switch mechanismbeing shown as in open position;

Fig. 5a is a fragmentary view illustrating cooperating parts of myswitch mechanism as the same is shown in Fig. 5;

Fig. 6 is a vertical sectional view taken on the line 6-5 of Fig. 2 andillustrating the manner in which the movable contacts are' pivoted tothe breaker arm;

Fig. '7 is a transverse sectional view taken on the line 'll of Fig. 6looking in the direction of the arrows;

Fig. 8 is a transverse sectional view taken on the line 88 of Fig. 6;

Fig. 9 is a perspective view of the movable contact actuating springassembly per se; and

Fig. 10 is a fragmentary plan view illustrating a modified arrangementfor seating one end of each of the switch loading springs.

Referring to the drawings and particularly to Fig. 1, a fragmentaryportion of an annular housing III for a gear reduction drive system of acontrollable pitch-change mechanism for aircraft propellers is shownwith an electrical switch H constructed in accordance with the inventionin cooperable relation therewith. As shown, the switch I l occupies achamber l2 defined or formed by a housing extension l3 of said housingIll. The switch [I is suitably secured to the housing If! by a pluralityof bolts it whereby it is operatively related to a cam base, disk ordrum l5 which carries a cam segment I5a, the drum [5 being rotatablymovable on its axis in response to movement of a low speed bell gear iiiin known manner.

In pitch-change mechanism as aforesaid, it is desirable that threeswitches of the character herein described and illustrated be employedto control the current supplied to a motor utilizable for driving saidpitch-change mechanism. Cne of these switches automatically opens thecircuit of said motor when the propeller blades reach a selectedlow-pitched position. Another of the switches automatically opens thecircuit of said motor when the propeller blades reach a selectedhigh-pitch position and the third of said switches automatically opensthe motor circuit when the propeller blades reach feather position.Moreover, in special applications, a fourth switch of the characterdescribed may be utilized to open the motor circuit when the propellerblades are moved to selected reverse pitch position. Each of theswitches is actuated by a cam segment IEa of the character describedabove, it being understood that the drum I5 carries a plurality of camsegments l5a which are suitably spaced around the periphery thereof, oneof these cam segments i5a being provided for each of the switches l lThe switch I! includes a block I! of insulation material which istransversely recessed on its underside, as at 18, to provide clearancefor a pair of fixed contacts is and 25) which are secured end- Wise inone portion of said block in side-by-side relation. Coactable with thefixed contacts 19 and 2B are the respective movable contacts 2i whichare operated in the manner hereinafter described.

Referring particularly to Fig. 8, a terminal member 22 is shown asdisposed within said recess Li and secured to the fixed contact ill, theterminal member 22 being connected to a screw threaded eyelet 23 lyingsubstantially flush with the outer face of the block l7. Anotherterminal member 24 also disposed within the recess H3, in

spaced relation to the terminal 22, is secured to the fixed contact and,similarly, is connected to a screw threaded eyelet 25 at its free endwhich is suitably supported at one side of the block ii.

A triangular metallic plate 26 having a pair of spaced protuberances '21formed thereon is suitably secured, as by a rivet 26a to the undersideof that end portion of the insulating block i! which is opposite the endportion to which the fixed contacts if} and Eli are secured, saidprotuberances 2'! being provided for a purpose hereinafter described.

The block of insulation material l! is secured between the bifurcatedend portions, respectively, of suitable supporting means which, asshown, comprises a pair of duplicate plate members 28 and 29. A plate23a of insulation material is in contact with the outer face of theplate 28 and, preferably, thin sheets 28?; of insulation material havinggreater area than the block ill are sandwiched between said block H andthe respective plate members, Figs. 7 and 8. In order to secure theseparts in assembled relation, I utilize a plurality of rivet pins 30, theoutermost two of which, Figs. 3, 4, and 5, pass through the plate 28a,the respective bifurcations of the plate member 28, the adjacentinsulating sheet 281), the block if the other insulating sheet 281) andthe respective bifurcations of the plate member 29. Below one endportion of the block H, a rivet pin 3!] extends through the plate 28a,the plate member 28, the two insulating sheets 28b, and the plate member29. In alinement with the rivet pin 38 last named, a rivet pin 38asecures together, on the one hand, the plate 28a, the plate 28 and theadjacent insulating sheet 28b, Fig. 3, and, another rivet pin 36bsecures together, on the other hand, the plate member 29 and theadjacent insulating sheet 28b, Fig. l.

The aforesaid plate 28a serves as an insulating support for the eyelet25 of the terminal member 24, Fig, 8. The opposite end portion of eachof the plate members 28 and 29 terminates in an arcuate, base-formingportion each of which has a plate 32 suitably secured thereto, Figs. 3-6inelusive. Each plate end portion and associated plate is apertured asindicated so that the switch ll may be secured to the housing ID by thebolts M as described above. One of the plates 32 comprises an inwardlyprojecting lip 32a utilizable as hereinafter described.

Referring particularly to Figs. 3-6 inclusive,

' the plate members 28 and 29, substantially in the central transverseplane of the switch, are shown as supporting a transversel disposedmember or pin 33 which supports a sleeve 33a secured at its oppositerespective ends to spaced ears 34a, 34a, (Figs. 2 and '7) integrallyformed with a rocker plate 34 which comprises an aperture 34b disposedbetween said ears. The rocker plate 34, at one end thereof, comprises alip 34c utilizable as hereinafter described. The rocker plate 34, at theother end thereof, comprises a cam-shaped actuating member 3403projecting from the lower surface thereof.

Disposed on the top surface of the rocker plate 34 above the actuatingmember 36d is a plate having, adjacent one end thereof, a pair of spacedpins 36, Fig. '7. The lower ends of the pins 36, for positioningpurposes, are received, respectively, in slots formed in the rockerplate 3 5, Fig. 2. Disposed on the upper surface of the plate 35 is anangle plate 3'1, a rivet 38 securing the plates 3'! and 35 to the rockerplate 34, Fig. 4. Th angle plate 3'! is formed from resilient materialand extends part way around a sleeve 39 carried by the aforesaid sleeve33a and terminates in an angular section 37a having projecting therefroma central tongue 312), Fig. 8, utilizable as hereinafter described. Theangle plate 31 further cornprises knife edges 31c disposed at oppositerespective sides of the tongue 31b.

Another plate 49 has a pair of spaced ears 413a, 411a at one endthereof, Fig. 7. The ears Mia are disposed inwardly of the respectiveears 34a and said ears 40a are loosel mounted on the sleeve 33a atopposite respective ends of the sleeve 39. The other end of the plate 40comprises a pair of spaced ears 40b extending therefrom in rightangularrelation, Figs. 1, 3, 4, 5 and 6. A pin 4 I, carried by the ears 40b,loosely supports a strip 42 of insulation material to which is suitablysecured a metallic strip 43 carrying, in suitable spaced relation, theabove described movable switch contacts 2!. The plate 40 is apertured asindicated at 40c and said plate 40, in the plane thereof, has a centraltongue 40d extending in this aperture. At opposite respective sides ofthe tongue 40d, the plate 40 comprises knife edges 406.

In accordance with the invention, a plate 45, preferably metallic, isshown as supported by the angle plate 3'1, the central tongue 31b of thelatter extending loosely through a central slot 45a formed in said plate45. A second plate 16, preferably metallic, has a central slot 46athrough which loosely extends the aforesaid central tongue Mid of theplate 40, the plate 46 having a central tongue 46b, Fig. 9. The plates45 and 36 support a coil spring arrangement ll? in the mannerhereinafter described and the aforesaid tongue 46b positions and locatessaid spring arrangement M with respect to said plates 45 and it.

Referring particularly to Fig. 9, the coil spring arrangement 41 isshown as comprising two coils il'a, l'ia which have a common axis. Theinner ends of these coils are connected together by an integralU-section 4117 and the central portion of this section is clamped by afolded portion Me of the plate 48. In generally similar manner, theouter ends of the coils 41a, 41a are connected together by an integralU-section 410, the central and two side portions thereof being clamped,re-- spectively, by folded portions 45b of the plate 45.

Referring particularly to Fig. 7, the pins 36 are shown as received inthe respective ends of a pair of coil springs d9, 39 which, at theirother ends, receive the hereinbefore described protuberances 21. As'will be'obvious, the springs d9 bias the pivoted system comprising therocker plate 34, the plate 35 and the angle plate 3? in acounterclockwise direction, Figs. 3 and 5.

In lieu of the plate 25 and its protuberances Zl, there may be utilizedthe modified arrangement shown in Fig. 10 for supporting the springs 49at adjacent ends thereof. Thus, as shown in Fig. 10, the plate 25 isomitted and an angular member 50 is provided, the latter having spacedprotuberances 5| which are received in adjacent ends of the springs 49.The member 58 may be fixed in position by riveting one end thereof tothe plate member 2 S at 52 and securing the other end thereof by one ofthe hereinbefore described rivets 30.

Referring particularly to Figs. 3 and 3a, the switch mechanism is shownin its closed position. At this time, the springs 49 are holding therocker plate 34 in such position that the lip 34c thereof is inengagement with one of the rivet pins 3t. Furthermore, at this time,some energy is stored in the coils 610., Ma of the spring arrangement41. As a result, the plate 55 is held in engagement with the set ofknife edges 31c and the plate i6 is held in engagement with the set ofknife edges 40c. As stated, the tongue 31b of the angle plate 31 isloosely received in the slot 45a of the plate 45. Similarly, the tongue48d of the plate M) is loosely received in the slot Mia of the plate 6.These tongues restrain the respective plates d5, 46 for pivotal movementwith respect to the angle plate 31 and the plate ii] during the opera...tions hereinafter described.

A component of the force applied by the spring arrangement M to the setof knife edges Mle is effective on the movable switch contacts 2! tohold them positively in engagement with the respective fixed contactsi9, 26. As a result, the circuit of the switch mechanism is closedbetween the eyelets 23 and 25, Fig. 8. Any circuit which is connectedthereto, for example, the circuit of the aforesaid pitch-changing motoris likewise closed, this circuit including the conductors 53 and 55, -8,which are connected, respectively, to the eyelets 23, 25.

Responsive to movement of the drum E5 in a counterclockwise directionfrom the position thereof shown in Fig. 3 to that shown in Fig. 4, thecam segment i'5a engages the member 3M of the rocker plate 34 and movesthe latter, while compressing the springs 49, clockwise to the positionshown in Figs. 4 and 4a. The angle plate 31 is secured to the rockerplate 3 for movement therewith as a unit and, accordingly, responsive tothe last named movement of said rocker plate 34, the angle plate 31',accompanied by some flexing thereof, moves clockwise from the positionshown in Figs. 3 and 3a to the position illustrated in Figs. 4 and 4a.The hereinbefore described plate 45 is connected to the angle plate 37by the tongue 31!) and, due to this connection, the described movementof the angle plate 3! causes the plates 45 and 46 together with thetherebycarried spring arrangement 4! to move in a counter-clockwisedirection substantially about axes defined by the respective sets ofknife edges 310 of the angle plate 31 and ine of the plate M, the

coil springs 41a. being wound to some extent and energy stored thereinduring the aforesaid movement of the angle plate 37.

As the parts are shown as positioned in Fig. la, the center of thehereinbefore described pin 33, the knife edges 310 of the angle plate 31and the knife edges We of the plate as are shown as disposedsubstantially in the same plane P. This is substantially one criticalposition of the sets of knife edges 31c and We. Durin the describedmovement of the parts as referred to above, the described switchcontacts remain closed under the influence of the spring arrangement 41.

In response to further slight movement of the drum H5 in acounter-clockwise direction beyond the position thereof shown in Fig. 4,the set of knife edges 310 of the angle plate 31 are moved slightly in aclockwise direction from the position thereof shown in Fig. do. As aresult, some of the energy previously stored in the end portion of theresilient angle plate ill becomes effective against the opposing forceof the spring arrangement 4'! to move the set of knife edges 37c beyondthe aforesaid critical position and, as soon as this happens, the coilslla of the spring arrangement 4'! become free to unwind to some extentand to release a part of the energy previously stored therein. As aresult, the plates 45 and it together with the thereby-carried springarrangement 41 continue the previously described movement thereof in acounter-clockwise direction substantially about axes defined by therespective sets of knife edges, this continuing movement, however,occurring in a snapping fashion. Resulting from this operation, theplate 40 is swung snap-like in a counter-clockwise direction to theposition shown in Figs. 5 and 5a to thereby move the switch contacts 2!snapfashion from the respective fixed contacts i9, 20 with resultantopening of the motor circuit. When the switch is open as shown in Fig.5, the plate 40, under the influence of the spring arrangement 41, isheld in engagement with a surface of the block ll, this surface actingas a stop to limit counter-clockwise movement of the plate 40.

In view of the foregoing, then, the switch is shown in open position inFigs. 5 and 5a. When the drum i5 moves to sufiicient extent in a clock-Wise direction from the position thereof shown in Fig. 5, the springs 49swing the angle plate 3'1, accompanied by some flexing thereof, in acounter-clockwise direction until, eventually, the sets of knife edges31c and tile are in alinement with the center of the pin 33. This issubstantially the other critical position of the sets of knife edges.The last described movement of the angle plate 31 causes the plates 45and 46 together with the thereby-carried spring arrangement i? to moveclockwise from the position shown in Fig. 5 substantially about axisdefined by the respective sets of knife edges. During this operation,the coil springs 41a are wound to some extent with resultant storage ofenerg therein. During the movement last described, the switch contactsremain open under the influence of spring arrangement 41.

In response to slight additional movement of the drum l5 in a clockwisedirection, some of the energy previously stored in the end portion ofthe resilient angle plate 31 becomes effective against the opposingforce of the spring arrangement l! to move the set of knife edges 37cbeyond the second critical position, and as soon as this happens, thecoils 41a of the spring arrangement 4'! become free to unwind to someextent and to release a part of the energy previously stored therein. Asa result, the plates 45 and 46 together with the thereby-carried springarrangement =3! continue the previously described movement thereof in aclockwise direction substantially about axes defined by the respectivesets of knife edges, this continued movement, however, occurring in asnapping fashion. Resulting from this operation, the plate 40 is swungsnap-like in a clockwise direction to the position shown in Figs. 3, 3a,4 and 4a to thereby move the switch contacts 2| snap-fashion intoengagement with the respective fixed contacts I9, 20 with resultantclosing of the motor circuit. It will be understood that, after the camsegment iila is disengaged from the member 3411 of the rocker plate 34,the springs 49 return the angle plate 3'! and parts secured thereto tothe respective positions shown in Figs. 3 and 6 wherein the angle platelip 340 is in engagement with the rivet pin 3! Fig. 3.

Referring to Fig. 1, it will be noted that a switch of my invention isshown as mounted in a housing extension I3 of the housing [0, the latterenclosing the gear reduction drive mechanism of the pitch-changingmechanism for an aircraft propeller. The switch H is so mounted in thehousing l3 that the engaging surfaces between the fixed contacts 18 and20 and the respective movable contacts 2|, when the switch is closedsubstantially coincides with a plane extending radially andlongitudinally of the housing it. During operation of the aircraftpropeller, the housing l rotates at high speed and, with the arrangementdescribed, the effect of centrifugal force is such that little or nopressure is applied to the cooperating switch contacts tending to openor close them. Likewise, when the movable switch contacts are open, theeffect of centrifugal force is substantially nil as regards any tendencyto close them. These are desirable features of the invention.

The hereinbefore described spring arrangement 4'! including the coils47a, 41a thereof serve in an. advantageous manner to cause the movableswitch contacts 2! to engage the respective fixed contacts l9 and 26under pressure which is adequate for the purpose intended, namely, themaintenance of close mechanical engagement between the respective setsof 00- operating contacts.

Another feature of the invention resides in the fact that the switch isof such character that the moving parts thereof have minimum mass. Evenso, due to the utilization of the described springs, little or novibration results during operation of the rotatable system.

Prior to the time that the switch mechanism of my invention is disposedin the housing extension [3, undesired pivotal movement of the rockerplate 34 in a direction away from the rivet pin 30 might occur undersome circumstances. It is for this reason that the lip 32a is providedon one of the plates 32, said lip 32a being engageable by the lip 340 ofthe rocker plate 34 under the conditions recited.

Although the switch mechanism of my invention has been illustrated anddescribed in connection with a particular application thereof, it shallbe understood that the invention is not to be thus limited. This is truebecause it will be obvious to those skilled in the art that my novelswitch mechanism has many applications other than the aircraft propellerart.

While the invention has been described with respect to a certainparticular preferred example which gives satisfactory results, it willbe understood by those skilled in the art after understanding theinvention, that various changes and modifications may be made withoutdeparting from the spirit and scope of the invention and it is intendedtherefore in the appended claims to cover all such changes andmodifications.

What is claimed as new and desired to be secured by Letters Patent, is:

1. In a snap switch mechanism of the character described, fixed andmovable contact means, a supported member, a plate supporting saidmovable contact means and being carried by said supported member infreely oscillatory relation, means comprising a spring arrangementconsisting of two coil springs connected together at their inner andouter ends respective ends being extended from the coils and one saidend engaging said supporting plate, and a member comprising a resilientend portion coactable with and movable past said supporting plate andengaged with the other end of said spring arrangement to operate thesame and impart snap-like movement to said supporting plate whereby saidmovable contact means is moved with respect to said fixed contact means.

2. In a rotating body, a snap action switch subject to centrifugal forceincluding a support pin on the body, a substantially centrifugallybalanced switch actuating member freely swingable on said pin, means forswinging said member about said pin, a resilient projection on saidmember having an outwardly facing abutment extending substantiallyradially outward from said pin and body in the direction of action, ofthe centrifugal force, a contact carrying arm swingable on said pin andextending substantially radially outward therefrom and in the directionof action of said centrifugal force, means including a fixed contactcooperable with the arm contact to establish swing limits for saidcontact carrying arm, said arm having an inwardly facing abutment facingsaid actuating member abutment, and spring means between said abutmentsurging them apart, said arm being swingable for switch actuationsubstantially independently of the effects of centrifugal force, througha limited arc of swing on both sides of the direction of act-ion on saidcentrifugal force.

3. In a rotating body, a snap action switch subject to centrifugal forceincluding a support pin on the body, a substantially centrifugallybalanced switch actuating member freely swingable on said pin, means forswinging said member about said pin, a resilient projection. on saidmember having an outwardly facing abutment extending substantiallyradially outward from said pin and body in the direction of action ofthe centrifugal force, a contact carrying arm swingable on. said pin andextending substantially radially outward therefrom and in the directionof action of said centrifugal force, means including a fixed contactcooperable with the arm contact to establish swing limits for saidcontact carrying arm, said arm having an inwardly facing abutment facingsaid actuating member abutment, and spring means between said abutmentsurging them apart, said arm being swingable for switch actuationsubstantially independently of the effects of centrifugal force, througha limited arc of swing on both sides of the direction of action on saidcentrifugal force, said spring means comprising a coiled spring whosecoil is displaced from said abutments having end portions extending fromthe coil and engaging said abutments.

4. In a rotating body, a snap action means subject to centrifugal forcecomprising an actuating member pivoted to the body for limited swinging,means for swinging said member, a projection on. said member having anoutwardly facing abutment swingable with the member throughsubstantially equal angles on either side of the line of action of saidcentrifugal force and passing through the member pivot, a switching armswingably mounted on the body at a pivot lying on a body radius passingthrough said member pivot, an abutment on said arm swingable therewithand facing said member abutment, and resilient means bearing on saidabutments and urging them apart, said member projection being elastic tobroaden the angle of swing through which said member must pass to carryits abutment over the spring centers defined by said abutments.

5. A snap action means comprising an actuattially equal angles on eitherside of a central l line passing through the member pivot, an armswingably mounted on the body at a pivot lying substantially on saidcentral line, said arm having an abutment facing said member abutment,and resilient means bearing on said abutments and urging them apart,said elastic member serving to broaden the angle of swing through whichsaid member must pass to carry its abutment over the spring centersdefined by said abutments.

6. A snap action means comprising an actuating member pivoted to a bodyfor limited swinging, means for swinging said member, a second memberpivoted to said body for limited swinging, said members being swingableto either side of a central line passing through said pivots, and

7. A snap action means comprising an actuating member pivoted to a bodyfor limited swinging, means for swinging said member, a second memberpivoted to said body for limited swinging, said members being swingableto either side of a central line passing through said pivots and havingfacing abutments spaced from their pivots, one of said members having anelastic portion between its abutment and its pivot deflectable in theplane of swinging of the member, and resilient means between and bearingon said abutments urging them apart.

8. A snap action means comprising an actuating member pivoted to a :bodyfor limited swinging, means for swinging said member, said member havingan abutment spaced from its pivot, an elastic portion between saidabutment and said swinging means to afiord angular displacementtherebetween upon force application to said swinging means, a secondpivoted member having an abutment spaced from its pivot, said twomembers being swingable to either side of a central line passing throughsaid pivots, and resilient means between and bearing on said abutment tourge them apart.

9. A snap action means comprising an actuating member pivoted to a. bodyfor limited swinging, means for swinging said member, said member havingan abutment spaced from its pivot,

said swingin means to afford angular displacement therebetween uponforce application to said swinging means, a second pivoted member havingan abutment spaced from its pivot, said two members being swingable toeither side of a cen- REFERENCES CITED The following references are ofrecord in the file of this patent:

UNITED STATES PATENTS Number Name Date 991,431 Duntley May 2, 19111,231,527 Long June 26, 1917 1,667,158 Ives Apr. 24, 1928 2,068,682Keefe Jan. 26, 193'? 2,199,974 Whitney May 7, 1940 2,230,720 Jarvis aFeb. 4, 1941 2,328,266 Durbin Aug. 31, 1943 2,390,365 Gofl" Dec. 4, 1945

